The present invention relates generally to sewing machines of a type which sews a string-shaped material, such as a tape or cord, to a sewing workpiece, such as a fabric, through lock switching. More particularly, the present invention relates to an improved sewing machine in which a large bobbin, capable of winding thereon a large amount of a string-shaped material, is controlled in orientation in response to rotation of a rotary member so that the string-shaped material can constantly be appropriately directed to a needle drop position.
Heretofore, there have been known sewing machines of a type which includes: a vertically-driven needle bar; a sewing needle fixed to a lower end portion of the needle bar; a rotary member mounted coaxially with the needle bar and freely rotatable about its axis; a bobbin having a string-shaped material wound thereon; and a guide member fixed to the rotary member for guiding the string-shaped material (e.g., string-shaped embroidering material, such as a tape or cord) to a sewing position or needle drop position of the sewing needle. The sewing machines of this type operate to sew the string-shaped material onto a fabric through lock stitching, by the rotation of the rotary member being appropriately controlled in accordance with a moving direction of the fabric based on embroidery data and by the orientation of the guide member being appropriately changed to optimize the direction in which the string-shaped material is to be guided to the needle drop position. In such sewing machines, the bobbin having the string-shaped material wound thereon is attached to the rotary member and the rotation of the rotary member is controlled in accordance with sewing control based on the embroidery data, in response to which the bobbin attached to the rotary member also rotates together with the guide member. With such movement, the string-shaped material can always be directed to needle drop position in an appropriate manner. However, with the aforementioned conventionally-known sewing machines, where the bobbin is attached to the rotary member, attachable or usable bobbins would be considerably limited in size due to the bobbin-attaching portion (i.e., portion of the rotary member); namely, it is difficult to use large-size bobbins such that great amounts of a string-shaped materials can be wound thereon.
One example of a sewing machine designed to avoid the above-mentioned prior art problem is known from Japanese Patent Application Laid-open Publication No. HEI-3-286797 (hereinafter referred to as “the patent literature”). Namely, the patent literature discloses a sewing machine of the aforementioned type, which can realize a size increase of attachable or usable bobbins by allowing a bobbin, having a string-shaped material wound thereon, to be disposed (or attached) above the needle bar. In the sewing machine disclosed in the patent literature, a bobbin, having a string-shaped material wound thereon, is adapted to be disposed on (attached to) a bobbin shaft supported at its opposite end portions on a pair of support members that are in turn fixed to a machine frame so as to extend upward from the machine frame. The bobbin shaft supports opposite end portions of the bobbin by means of a pair of retention members provided on the bobbin shaft. In this manner, the bobbin, having the string-shaped material wound thereon, can be disposed at an upper position away from the needle bar, rotary member, etc. independently of the rotary member. Thus, bobbins to be used can be increased in size, and thus, increased amounts of string-shaped materials can be wound on the bobbins.
The conventionally-known sewing machine disclosed in the patent literature can achieve an increase in size of bobbins to be used, by disposing a bobbin, having a string-shaped material wound thereon, at an upper position away from the needle bar, rotary member, etc., as set forth above. However, in the sewing machine disclosed in the patent literature, the bobbin is fixedly disposed at the upper position so that its orientation is uncontrollable, although the rotary member can be rotated when the string-shaped material is to be sewn onto a sewing workpiece, such as a fabric. Thus, in a case where the rotary member is rotated through 360 degrees or over in accordance with sewing control based on embroidery data, for example, the string-shaped material paid out from the bobbin may undesirably wrap around a machine head and get entangled. In order to avoid such an inconvenience, there is a need to create in advance embroidery data such that the rotary member does not have to be rotated through 360 degrees or over. However, if the rotation of the rotary member is limited like this, there would occur another problem that patterns capable of being formed on a sewing workpiece are limited considerably.
Further, in the prior art sewing machine disclosed in the patent literature, the bobbin is disposed high above the machine head. This means that, at the time of mounting the bobbin to the machine, a human operator has to lift up the bobbin high above the machine head. However, a large-size bobbin having a large amount of a string-shaped material wound thereon would increase in weight, and thus, the operation for lifting up such a large-size, heavy-weight bobbin high above the machine head would undesirably require an extremely great force of the human operator and thereby impose a great load on the human operator.